1. Field of the Invention
The present invention relates to an apparatus for removing volatile material from solids. More particularly, the invention relates to an apparatus for removing hydrocarbons from earth, dirt, rock cuttings, drilling mud and similar materials. Still more particularly, the invention relates to an apparatus including a heating means, a fluidized bed, cyclones and fluid circulation means for separation of hydrocarbons and removal of solid material.
2. Related Information.
It is a vital environmental concern that the volatile material be removed from granular solids; i.e. the hydrocarbons must be removed from earth, dirt, and similar materials. The removal of hydrocarbons that have soaked into the ground over a period of time is now known as "remediation" and the number of recognized sites has grown astronomically. Former refinery and chemical manufacturing and storage facilities are typical sites of such work. Even the location where a gasoline service station once stood is a candidate for "remediation." Other locations where remediation may be desirable or required are dry cleaners, junk or storage yards, automobile-related businesses and garbage dumps.
An area of particular application of the instant invention, in which volatile materials must be removed from granular solids, is the reclamation of petroleum lubricated drilling fluids used in the exploration and production of petroleum oils. The drilling fluid, referred to as "mud," serves several purposes, the most important of which includes cooling and lubricating the bit and removing drilled solids, or cuttings, from the bore hole. While it is essentially a water based, fluid composition, the drilling mud is frequently compounded with a lubricant material such as diesel, crude oil or other non-water petroleum based constituent to facilitate the mud's lubricating characteristics.
The mud is usually contained in a mud pit, which is connected by way of a mud line and mud pump to a hose and swivel used to inject the mud into the top of the drill pipe. The returning mud, combined with the cuttings, is captured in a mud return pipe and recirculated through the drill pipe.
When the concentration of the drill cuttings in the mud rises too high, recirculation of the mud becomes a problem. In order for the mud to perform its several functions, its viscosity, density and other properties must be maintained within acceptable limits. The drill cuttings adversely affect these properties thus reducing the carrying capacity and lubricating ability of the mud, possibly damaging the drilling equipment.
To allow for effective recirculation, the mud is usually separated from the cuttings prior to being recycled through the drill pipe. The cuttings are then disposed of as waste. This presents problem when the lubricating properties of the mud have been enhanced by the addition of hydrocarbons. Because of the hydrocarbons mixed in with the cuttings, a hazardous waste problem is present. Upon completion of the use of the mud in the well, the mud itself becomes waste that must be remediated for the same reasons.
Historically, the contaminated cuttings and mud were diluted by mixing, and hauled to remote sites for disposal in landfills. This, however, also presents a problem in that the landfill then becomes a hazardous waste site, possibly leaving the dumper liable for environmental damages indefinitely.
Decontaminating the materials is the more environmentally attractive option. Treatment processes heretofore available to remove oil or other hydrocarbons from cuttings and mud include distillation, solvent washing, and mud burning. While these processes are effective to varying degrees at stripping the hydrocarbon contaminants from cuttings and mud particulates and rendering them environmentally clean, the processes remain problematic in that of disposal of the liquid or vapor from the disassociated contaminant.
There are several patents that disclose technology related to rotary kilns specifically designed to remove volatile hydrocarbons from solid material such as soil. See, for example, U.S. Pat. Nos. 5,152,233; 5,199,354; 5,302,118, and 5,378,059. All of the rotary kilns are gas fired with the hot combustion gases being directed into the drum to heat the solids. Unfortunately, when the solids have a substantial quantity of hydrocarbonaceous material an explosion hazard may be present. In an addition environmental hazard, when a flame is applied directly to the solids, the contaminants are oxidized and turned into smoke and other forms of air pollution. This process prevents recycling of the hydrocarbons for reuse in the same or similar drilling operation.
What is needed is a method by which the hydrocarbons used in the drilling operation may be separated from the mud taken from a drilling site. Once separated, the hydrocarbons could be safely recycled into the same drilling site, thereby preventing environmental damage and also reducing the cost of hydrocarbons required during the drilling process. When the drilling was completed, the hydrocarbons could be relocated to a new drilling site for reuse and further recycling.